Long tube vertical evaporator



Filed Jan. 4, 1954 FIG. 2

FIG.

INVENTOR. RALPH E. BERGSTROM W ATTORNE United States Patent F LONG TUBE VERTICAL EVAPORATOR Ralph E. Bergstrom, Chicago, 111., assignor to Whiting Corporation, a corporation of Illinois 7 Application January 4, 1954, Serial No. 401,874

5 Claims. ca. 159-46) My invention pertains generally to evaporators, and more particularly to a long tube vertical evaporator having both liquid heating tubes and liquid evaporating tubes disposed within a single shell or body. 7

Long tube vertical evaporators generally utilize an upright tube bundle enclosed by a shell into which a condensible heating fluid, usually steam, is introduced. The liquid to be evaporated may be first passed through an externally disposed heater and then into the tube bundle where boiling and evaporation occurs, the vapors so generated being discharged into a vapor head above the tube bundle. In other instances, the necessary heating of the liquor is accomplished within the evaporating tubes, eliminating the external heater, but requiring a larger tube bundle in the evaporator body. Ordinarily a bafiie is mounted in the vapor head above the tube bundle to deflect into a suitable drain any liquid particles emerging from the evaporating tubes. It has been found in operation, however, that a certain amount of the liquid collected on the lower surface of the bathe will fall back into the evaporating tubes and there create undesirable changes in liquor concentration.

One of the important objects of my invention is the provision of a long tube vertical evaporator of greater efiiciency which incorporates within a single shell a set of heater tubes and a set of evaporating tubes, each set of tubes being adapted for operation in series at optimum velocity.

Another important object of my invention is the provision of a long tube vertical evaporator and heater unit which occupies less floor space than that ordinarilyrequired and which renders unnecessary a portion of the accessory equipment normally disposed externally to the evaporator.

A further important object of my invention is the provision of a long tube vertical evaporator which is more eflicient than the type now in general use, which is less costly, and which reduces the amount of fall backof liquor into the evaporating tubes from the baflie.

Additional objects of my invention reside in various sub-assemblies and the relation and proportions existing between the various components, all of which are fully explained in the following description and illustrated in the appended drawing, in which:

Fig. 1 is a schematic elevation of a long tube vertical evaporator incorporating my invention.

Fig. 2 is a horizontal cross section taken on the line 22 of Pig. 1.

In brief, my evaporator employs a generally cylindrical tube bundle mounted in a shell. The center set of tubes in this bundle is employed solely for heating the liquor, suitable connections being provided for causing the incoming liquor to flow up one portion of this set of heater tubes and down the other portion. Upon emergence from the heater tubes the liquor is distributed to the evaporator tubes in which it is vaporized, these latter tubes being arranged circumferentially around the heater tubes. A

2,741,303 Patented Apr. 10, 1956 2 bafiie is provided in the vapor head and extends over the upper ends of the tubes.

To obtain eficient liquor heating, the velocity of liquor flow in the heater tubes must be substantially greater than the velocity of liquor flow in the evaporating tubes. It is therefore essential that the total cross-sectional area of the heater tubes employed to carry the liquor in one direction be less than half the total cross-sectional area of the evaporating tubes, and better results will be obtained if this ratio is further reduced, as for example, 1:5, 1:100 or 1/250. By properly selecting this ratio, both the heater tubes and the evaporating tubes may be operated at optimum velocity, thereby substantially improving the eiiiciency .of the device. Heat losses by radiation may also be reduced in comparison to some con: ventional evaporators, since the total exposed area of my shell is less than the total exposed area of a conventional shell plus the exposed area of the conventional heater and interconnecting piping and accessories. Furthermore, the rate of liquor fall back into the evaporating tubes is reduced since there are no evaporator tubes disposed below the center portion of the bathe.

Referring to the drawing, I have illustrated a long tube vertical evaporator having a shell 10 adapted for operation in an upright position. ,Arranged around the upper portion of the shell 19 and communicating therewith is a catchall body 11 having a steam inlet 12. The catchall is generally cylindrical in shape and may be provided with a drain 13 near its lower extremity. The passageway 14, which interconnects the catchall 1 1 with the shell 11?, is disposed near the upper extremity of the catchall and preferably above the level of the steam inlet 12. A condensate drain 16 is provided near the lower extremity of the shell 10.

An upper tube sheet 17 and a lower tube sheet 18 are,

sealed to opposite ends of the shell 10. A set of upright heater tubes 19 extends through the center portions of the tube sheets '17 and 18 and are surrounded by circumferentially arranged evaporating tubes 21, which also extend through the sheets 17 and 18. A dished bottom 22 is sealed to the lower end of the shell 19 and the lower tube sheet 18, providing interconnection between all of the evaporator tubes 21. A liquor inlet 23 may extend through the dished bottom 22 and communicate with half of the heater tubes 19. A cap 25 is sealed to the upper tube sheet 17 across the upper ends of all the heater tubes 19 and may additionally be utilized to support a baffle 24 extending laterally over the evaporating tubes 21. A

vapor head 26 having a drain 27 extends around the baffle 24 and is sealed to the catchall 11 in conventional manner.

In operation, steam is introduced into the shell 1!) through the steam inlet 12. The liquor tobe evaporated is introduced through the liquor inlet 23 and flows upwardly through approximately one-half of the heater tubes 13 into the cap 25, then downwardly through the remainingheater tubes 19 into the bottom 22. From this all the liquor rises in the evaporating tubes 21 where evaporation takes place, the vapor being discharged from the open upper ends of the evaporating tubes 21 against the bafiie 24. As previously noted, it is essential to efficient operation that optimum velocity of liquor flow be maintained in the heater tubes 19 and in the evaporating tubes 21, the former velocity being substantially greater than the latter. This I accomplish without the aid of pumps or other accessory equipment by limiting the ratio of cross-sectional area of the heater tubes employed to carry liquor in one direction to the total cross-sectional area of the evaporating tubes. It is essential that this ratio be not greater than 1:2 and preferably should be less than 1:10, that is, the total cross-sectional area of the heater tubes 19 employed to conduct the incoming the combined cross-sectional meant the evaporating tubes. 'For all practicalpurposes'the upper limit ofthe acceptable range of the ratio may-be regarded 'as being one in which the total cross'section'al area of the t-Wosets of heating tubes-is substantially less than one-quarter of the total cross'sectional area of the evaporator tubes.

By obtaining an adequately high velocity in the heater tubes the formation of a'fihn resistant to heat transfer along the internal surface "of the tube is inhibited. In addition, boiling'of the liquor. within the'heater tubes is virtually eliminated. *By'virtue of the improved efficiency of "mydevice, less'total' 'heating surface-is required than that conventionally considered essential for a given rate of evaporation. converselypwith the sanze' heating surface greater evaporator capacity can be obtained by utilizing the'structnre described.

It will be noted that "the cap 25 is centrally disposed with respect to the bafiie and that theevaporating tubes 21 are disposed bElOWthQ'PCl'lPhEI'Q-lpOilIlOl'i of the baiiie 24. The rate'atwhich liquid collected on' the lower surface'ofthebaffle24 falls back intothe evaporating tubes varies directly with the distance the liquor must travel q along the baffieto-reach the extremity of the bafile. Since the central'portion of the baffle .24 is not employed for this purpose, the rate of "liquorfallback intothe'evaporating tubes 21 is reduced. 7 7 By utilizing my invention. the need .for an heater "is obviously limited; This also eliminates the i upwardly (when-the twoeets-ofheater tubesare of equal cross sectional area) should be less than 1/10 lower-ends of the tubes19. It is alsonconternplatedibat.

the set of heater tubes 19 may be disposed in positions other than the central portion of the tube bundle. The ratios of cross-sectional area between the heater tubes 19 and the evaporating tubes 21 may be obtained by control or" the number of tubes employed, or by the internal diameter of the tubes, or both, as required by circumstances.

I claim: V

1. An evaporator-comprising a shelL means forpassing a heating fluid into the'shell, two-setsofheating tubes 7 and one set of evaporating tubes within the shell, the

external exposed piping required to connect the heater with the evaporatorbody and with a source of ste'amywhich-in turn not only *reduces the cost and the minimum floor space required but also reduces thei'total exposed surface 'area-through'which heat maybe lost by radiationto the atmosphere; V I V In comparison with conventional *evaporators not using an external heater, 'I :ca n reduce 'the total-number of tubes required to 'ac corrrplish'the workgand thereby "use ajsmaller :shell andlessjfloor'space. In addition, the

" initial cost ,is alsoreduced,,ortorsubstantially the same.

cost'as aconventionalevaporator, increased-cap acity may be obtained; I 7 a V V 7 These 'advantagesmay "be illustrated by a'specific problem. For' example-'assnme it is--desired to heat '110;44j0

pounds per hour of liquor having 24%"totalso1ids and a specific heat'of 0.84'from' 201*F. toj.224 F. using st'eam at 246 or'iabout :13 pounds gauge pressuregand' toevaporate 26,900 pounds fromithe liquor; "Using 2 inchOf'D. steel tubes 27 'feeflong Witha'WalIthicknesSofOlZS in,

and arranging theheating tubes in two ,passes would re-, 'quire 22'tubes inthe heating portion'and 468 tubes inthe evaporating portion, or a total of 490 tubes. 1A conventional evaporator without a heater, using identicaltubes',

would "require 580 -tubes ito "accomplish the 'same Work.

The arrangement described and illustrated constitutes an embodiment of my invention, but it should be understood it may be altered in'various ways as required by circumstances, For'exan plmany number of passes may be'employedin-theheater tubes 19'1by suitably arranging the 'cap 25 andproviding-the necessary connections at the total cross sectional area of the two sets of heating tubes being substantially lessthan one-quarter the total cross sectional area of the evaporating tubes, a vapor head sealing the top of the shell and a bottom sealing thelower.

end of the shell, means at the top of said tubes establishingco'rnmunication between the two'sets of heatingtubes and other means at the top of said'tubes establishing com- I munication between the evaporating tubes and the vapor head, aliquid inlet atthe 'bottom'oi ene set of said heating tubes and means at the lower ends oi said tubes' establishing communication between'said bottom and the other set of heating tubesand between the evaporatingrtubes and said bottom, whereby liquid introduced CIIOHgh SBi'd inlet will flow at relatively high velocity "up through said first set of heating tubes-and 'down through said 'se'cond set and thence upwardly at relatively-lowyelocity through saidset of evaporating tubes.

2. 'The structure defined in claim l-in which the two sets ofheating tubes are positioned substantially eentrally within the .she-llend are surrounded by the set of evaporating tubes. V

3. The structure defiued in claim -l-including a ba'ifle mounted on the means at the topofthe tubes establishing" commnnication'between the two sets ofheating tubes and extending over and spaced from the upper 'ends of evaporating tubes for facilitating separation of vapor from liquor in fluid impinging against said "bafiie. V

4. The structure defined in clairn l n which the total cross sectional area'of each set of heating tubes is less than one-tenth the to-tal cross sectional area of the evapcrating tubes.

5. The structure deiinedin claim 1 including a :g'enerally horizontal baflle disposed above the tubes extending radially-over :and spaced from the upper=zends of the evaporating tubes for facilitating separation of vapor from liquor inifluidimpinging againstsaid baflie;

References ilited'in therfiie TOfI this lpatent' UNITED STATES PATENTS 

